Whiplash related injuries are caused by the rapid acceleration of a person's cranium and cervical spine, which occurs, for example, in an automobile collision. The rapid acceleration causes the extension and flexion of the cervical spine which, in turn, can cause severe injury. Types of whiplash related injuries include fractured and/or dislocated vertebrae, torn ligaments (both anterior and posterior of the spinal column), and avulsion of parts of the vertebrae, ligaments and intervertebrae discs.
It has been found that the C4, C5 and C6 cervical vertebrae, and the paravertebrae ligaments are most often damaged with whiplash related injuries, although the entire cervical spine may well be involved. Rapid hyperextension of the cervical spine can stretch the anterior longitudinal ligament, thus placing it in traction and causing either bone or ligamentous damage. Such hyperextension typically damages the C1 through C cervical vertebrae. The vertebral artery, which extends through an opening in the vertebrae, and the sympathetic nerve fibers that surround the artery are also often damaged. These types of injuries cause severe disabilities and, in some instances, death.
Seatbacks and/or headrests in automobiles, trucks, and other types of vehicles are provided to prevent whiplash related injuries to passengers during collisions, but typically fail. During a rear-end vehicle collision, the forces of the collision typically cause a passenger's cranium and cervical spine to rapidly accelerate toward the rear of the vehicle. Once the cranium strikes the seatback or headrest, it then rapidly accelerates in the opposite direction toward the front of the vehicle. The rearward acceleration of the cranium, and resulting collision with the seatback or headrest, causes hyperextension of the cervical spine and, thus, typically injures the anterior structure of the passenger's neck. The forward acceleration of the cranium, on the other hand, causes hyperflexion of the cervical spine and typically injures the posterior structure of the neck.
One problem with known seatbacks and/or headrests is that the surface intended to stop the movement of a person's head and neck is typically flat, or does not correspond to the posterior contour thereof. As a result, during a rear-end collision, typically the back, or posterior portion of the cranium is the first portion of the passenger's body to strike the seatback or headrest. However, the cervical spine, which is located inferiorly with respect to the posterior portion of the cranium, continues to move toward the headrest. As a result, the cervical spine is forced to move relative to the cranium which, in turn, causes severe vertebral damage.
Also, the top surfaces of many known headrests are located at about the same height, or below the height of a passenger's ears, which is normally about the center of gravity of the head. When a passenger's cranium is forced against such a headrest during a collision, it often slides upwardly over the top edge of the headrest. As a result, the cranium is stretched upwardly relative to the cervical spine, typically causing further vertebral damage.
It is an object of the present invention, therefore, to overcome the problems and disadvantages of known apparatus for preventing whiplash, such as vehicle headrests and seatbacks.